The European Space Agency’s Rosetta mission successfully landed the Philae space probe on the surface of the comet 67P/Churyumov-Gerasimenko, just after 5am (NZT) this morning.

Image taken by Philae at about 3km away from the comet, with part of its landing gear seen at top right.Credit: ESA/Rosetta/Philae/ROLIS/DLR

The mission’s attempt to land on the giant ball of ice and dust, whizzing past at 66,000 kilometers per hour, has had scientists waiting more than a decade and is said to be one of the most audacious space exploits ever.

While comets seen crossing the night sky have evoked fascination and fear for millennia, today scientists are interested in how they may have helped shape our planet. One theory is that they delivered water, carbon and other essential building-blocks for life to the early Earth.

The ice and rock that make up comets preserve molecules, acting like a time capsule carrying material from billions of years ago. However, their extreme speed and distance have made them difficult to investigate, with previous missions only being fly-bys – brief encounters crossing a comet’s path to gather data or collect samples of dust.

Now that the Philae probe – specifically designed to take samples from the surface of the comet – has hitched a ride, scientists hope that the data it collects will shed light on how planets and life are created.

The SMC collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).

NEW COMMENT: Mr Alan Gilmore, former Resident Superintendent at Mount John University Observatory in Tekapo, comments:

“Landing on a comet nucleus is an immense achievement. There have been several flybys of comets, beginning with the European Space Agency’s Giotto mission to Comet Halley in 1986. This is the first time a long-duration study of a comet nucleus has been attempted. This will allow detailed sampling of the stuff that comets are made of. It will tell us if comets brought water and complex chemicals to the early Earth.

“There are extraordinary difficulties in making such a landing. The comet nucleus has little useful gravity so the lander has to be pre-programmed to home in on the landing site. The only similar attempt was the landing of a sampler from the Japan’s Hayabusa spacecraft on the asteroid Itokawa in 2009.”

“The successful landing of the Philae probe on a comet is a spectacular success for the European Space Agency. To be able to design and launch a vehicle that has an ultimate objective to land on such a small and distant object a decade later is a great testament to human engineering. The data collected by the probe and its parent satellite, Rosetta, will be of great value to the scientific community for decades to come. Part of the difficulty of this mission is that the gravity of the comet is very low and the material it’s made of is unknown and potentially very soft, in fact we often describe comets as ‘dirty snowballs’. This means that it will be hard to keep the Philae probe on the surface, but even if that’s the case that will provide valuable scientific data on the composition of comets.

“For me personally it absolutely amazing to see how projects like this capture the imagination of the entire world and bring people together – this is not an achievement just of one space agency, but of humanity! It’s just a great feeling to see how excited people are about space science on a global scale today. NZ company Rakon supplied parts of one of the experiments on Philae – the crystal oscillators and crystal filters in the CONSERT sounding experiment which will hopefully tell us about the comet core, so today there is even a small part of NZ on a comet millions of kilometres from Earth.”

“It is incredible how things can be calculated and planned in advance! Our ESA colleagues started designing this space flight some 15 years ago. The mission was launched successfully 10 years ago; it made several orbits around the Sun, twice it passed near the Earth getting necessary acceleration from its gravitational field to go as far as the orbit of Mars. It passed near Mars getting necessary speed to go as far as the orbit of Jupiter. Finally, it made manoeuvres to approach the comet and start moving on a synchronous orbit creating a beautiful duet. There was the moment of truth when it had to wake up after 10 years of flight, the flight based only on theoretical calculations, without control or intervention from the Earth. Then it took amazing (!) pictures of the surface of the comet.

“My colleagues and I followed every stage of the last 24 hours: Go/NoGo exercises, manoeuvres, separation, and finally landing! Incredible! I feel I am so lucky living at this time, so lucky being an astronomer at this fantastic Golden Age of Astronomy. There will be a huge scientific and technological impact of this mission, but there is another component in it – philosophical, human, and overall, I think it is really “one giant leap for mankind!” Massive congratulations to my colleagues at ESA.”

“The Rosetta mission has been a tremendous adventure for the European Space Agency and the scientists involved. It has already proved to be a scientific success and promises to deliver much more over the next months and years. The riskiest part, landing the Philae spacecraft on the surface of the comet, has never been done before and I would like to send my congratulations for this amazing achievement. We look forward eagerly to the images and scientific results from the lander.”

Prof Jeffrey S. Kargel, Department of Hydrology & Water Resources at the University of Arizona, comments:

“The engineering achievement of the Rosetta mission has been nothing short of amazing. The landscape and complex geology of Comet 67P is way beyond my wildest imagination of what a comet nucleus could look like. The cratered, fractured, boulder-strewn surface and towering pinnacles of ice attest to tumultuous activity of jetting gases, and solar-heat-driven erosion of ice and collapsing mountains of ice. These mountains are made of ice as we know it on Earth, but there is also a noxious stew of frozen carbon monoxide, carbon dioxide, ammonia, formaldehyde, and methyl alcohol. Comets are noxious to us, though they are made of the kind of material that may have helped bless Earth with life 4 billion years ago by supplying some of the basic organic compounds and reactive gases that could have helped initiate the first living things on our planet. It’s a wild little world, and the Rosetta orbiter and its Philae lander have set our eyes and imaginations on this distant land, to explore it like no comet has ever been explored before. Landing should be taking place right about NOW!”

Dr Jen Gupta, outreach officer at University of Portsmouth Institute of Cosmology, explains the significance of today’s Rosetta mission, comments:

“The European Space Agency Rosetta spacecraft successfully released the Philae lander earlier today for its seven hour freefall descent to the surface of Comet 67P/Churyumov-Gerasimenko. Philae is expected to land on the comet at around 15.35 GMT, however because it is so far away (between the orbits of Mars and Jupiter) it will take the radio signals 28 minutes to get to us on Earth. This means that we are expecting confirmation of the landing at 16.03 at the earliest.

“The mission has had some drama over the past 24 hours. Last night Philae didn’t quite switch on correctly so they had to switch it off and on again! Everything was going well but this morning it was reported that its thruster is out of action, which means that Philae will have to rely on harpoons and ice screws to stay on the surface once it lands. There is still uncertainly over what the surface will be like on landing – it could be hard rock or powdery dust.

“The Rosetta mission was launched in March 2004 and has taken 10 years to get to its destination. It went into orbit around Comet 67P on 6th August 2014, the first time a spacecraft has orbited a comet. Today is the first time that anyone has ever attempted to land a robot on a comet. Comets are essentially dirty snowballs left over from the formation of the solar system and give us an insight into what the solar system was like 4.5 billion years ago when the planets were forming. It is possible that comets brought water to the surface of Earth and possibly even the building blocks of life.

“Rosetta and Philae will help us to understand these icy bodies as they accompany Comet 67P on its journey towards the Sun. You can follow the missions on twitter at @ESA_Rosetta and @Philae2014 and today’s landing attempt on the hashtag #CometLanding.”

“No matter what happens in the next hour, today will mark a change, a point of reference in the history of space science. I feel so lucky and honored to be a part of it.”

Prof John Zarnecki, Emeritus Professor of Space Science at the Planetary & Space Sciences Research Institute, The Open University, said:

“I’m currently waiting expectantly at ESOC in Germany for the today’s landing of Philae on comet CG. I have a strong sense of déjà vu, as I was here in 1986 as Project Manager for one of the instruments on Giotto which spectacularly flew past Halley’s Comet. Then I was here again in January 2014 as lead scientist for the Surface Science Package where I monitored the dramatic descent and landing of the Huygens Probe onto the surface of Saturn’s largest moon Titan.

“Today I’m hoping to make it third time lucky! Fingers Crossed!”

Prof Ken Pounds, Emeritus Professor of Space Science at the University of Leicester and CEO of PPARC from 1994-98, comments:

“Rosetta is already a remarkable demonstration of how European capabilities in space science have grown over the 50 years since the formation of the European Space Research Organisation (ESRO) in 1964 – with the UK as primary funder. The UK was also a key player in the foundation of ESA 11 years later (particularly through Michael Heseltine’s role), although – importantly – for a further decade space science continued to be dominated by NASA.

“The current position, in which Europe is a world leader in many areas of space science, has its origins in the decision taken in 1984 (advocated by the UK and Germany) for ESA to set down its long-term science priorities. Under the leadership of Roger Bonnet, the resulting ‘Horizon 2000’ programme transformed Europe from a bit player to a world leader in many areas, including solar physics, cosmology and X-ray Astronomy.

“Rosetta was one of the new missions in the H2000 programme. Against substantial competition, the Particle Physics and Astronomy Research Council was sufficiently inspired by the technical and scientific challenge of this ‘comet chasing mission’ to approve UK participation in 1996.

“Seeing a comet up-close as it approaches – and then recedes from – the Sun over the next 18 months will be exciting enough. A successful touch down of Philae will be a bonus few would have bet on all those years ago.”

“Excitement is really building now following the successful separation. Over the next few hours, vital measurements and images will be taken by both the orbiter and lander. We’re particularly keen to see if our predictions of nucleus charging are accurate, and to find out more about the plasma environment following our pioneering work with Giotto in 1986 and 1992. But the overwhelming feeling is one of anticipation and hope that 20 years of work on the mission will include a successful landing today.

“ESA just confirmed that telemetry is being received from both lander and orbiter following separation – this is an important step, and there were a tense few minutes awaiting the confirmation.”

Dr David Clements, Astrophysicist at Imperial College London, comments:

“Rosetta is a hugely ambitious European mission that already is a great success. The Philae lander is even more ambitious – a truly mould-breaking endeavour. Whether the landing is a success or not, to have merely been in a position to attempt it is an astounding achievement.

“I may be an extragalactic astronomer, working on things millions of times further away than Rosetta and comet 67P, but everyone I know, whatever area of astrophysics they work on, has been inspired by what Rosetta is doing.”

[Declared interests: “I’m employed by Imperial College London which has a research group, not my own, working on Rosetta; STFC funds my research as it funds Rosetta work; I have worked and am working on other ESA missions; I have a book on Infrared Astronomy about to be released that includes a short section on comets.”]

“If today’s landing goes well, Rosetta will tell us if comets made our planet blue by providing the oceans.

“This is the most difficult landing in space history, like landing a balloon in a city centre on a windy day with your eyes closed.

“Did comets deliver the building blocks of living things and start life on Earth? We may soon know with the help of Rosetta.

“Some scientists gave spent twenty years working on this mission. The fate of all that work lies in the final few seconds of touch down.”

Earlier commentary from the AusSMC:

Professor Geraint F. Lewis, Sydney Institute for Astronomy in the School of Physics at The University of Sydney, comments:

“Comets hold the secrets to the birth of the solar system being left over debris of the material that built the planets, including the Earth.

“For the first time, Earth will land a space probe on the surface of a comet, with Rosetta due to touch down on Comet 67P in the next few hours.

“When safely anchored in the extremely weak gravity, Rosetta will start to scratch the surface to reveal the complex chemistry of the cometary surface. We expect to find a lot of water, frozen as ice, but also a soup of chemicals that must have rained down on the early Earth. These chemicals, especially the water, could have proved vital for the eventual formation of life on this planet.”

Dr Alan Duffy, Research Fellow and an astronomer at Swinburne University of Technology, comments:

“The European Space Agency managed to get the Rosetta spacecraft to within 100km of their target comet Churyumov-Gerasminko (67P) after a 6 billion km journey. This is equivalent to hitting a bullseye in Perth from Sydney with a billion dollar dart. Blindfolded. As for the majority of the trip the craft was powered down travelling on the trajectory blind. It was a nervous wait to see if it would ever start up again. There was a lot of celebration on August 7th when ESA sent the successful “wake-up” call from Rosetta over twitter yet the hardest part of the entire mission was still to come.

“Rosetta has spiralled around the comet taking evermore detailed pictures in order to find a perfect landing spot for its lander Philae. The first big surprise was that the comet is more like two large pieces joined together, looking at times like a cosmic rubber duck, with the lander’s target on the crown of the ‘head’.

“Unfortunately the surface couldn’t be less inviting, with sharp, lander destroying rock and ice shards all over the surface making the landing fraught with danger.

“Rosetta will approach to within just 20km of the mountain sized frozen comet and drop the lander Philae onto it. It will be a slow fall, lasting 7 hours and without thrusters means that there’s no chance to change course if a lander-destroying shard of ice and rock is underneath.

“As a result of the enormous distance from Earth the signal will take too long from ESA’s space operations centre in Darmstadt meaning the entire historic journey will be automated. ESA will push a button and have 7 agonising hours to watch if the fridge-sized Philae lander makes history with the first ever soft landing on a comet.

“The craft will try to harpoon itself onto the surface as the comet’s gravity is so weak it could bounce off into space.

“If successful the craft can drill into the surface of the comet, taking unique samples of a material that came from the time when our solar system first formed. A frozen fossil of the material that the planets formed from billions of years ago.

“Over the next few months comet Churyumov-Gerasminko will heat up as it gets closer to the Sun, causing the ice to boil off into space forming the comet’s tail, and will be a spectacular final unique image for the Philae lander.”

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